1. Field of the Invention
The present invention relates to a display control apparatus and a display control method in which a plurality of images are displayed on the same page.
2. Description of the Related Art
To display images with an image reproduction apparatus, the following method is generally used: a reading device reads image data directly or otherwise (e.g., communicatively) from a medium having images recorded therein; the image data is stored in a displayable form in a temporary memory device; the image is then displayed. Here, the task of reading the images via the reading device generally takes much time compared to the speed of reading the images from the temporary memory device. This is due to factors such as the difference in data transfer rate between the nonvolatile memory having the image data recorded therein and the temporary memory device, and the necessity of a decoding process before the compressed images are read in a displayable form into the temporary memory device. As such, when a user successively switches between displayed images, the reading task of the reading device may fail to keep up with the pace of the user's operation. Therefore, methods of predicting images to be displayed and reading the images in advance (pre-reading) have been proposed.
In such image pre-reading, how to pre-read appropriate images quickly is important. Exemplary conventional pre-reading approaches include the following. A technique described in Japanese Patent Laid-Open No. 2007-306291 (hereinafter referred to as document 1) uses an approach in which a plurality of images displayed in a screen are patched together and held as one image for image display according to the display size to thereby reduce the image reading time. A display control apparatus in Japanese Patent Laid-Open No. 10-63455 (hereinafter referred to as document 2) uses an approach in which, in order to allow swift switching between pages, a page that is likely to be displayed next is predicted, pre-read, and stored in memory.
However, if switching of the screen by a user operation is too fast relative to the reading time, pre-reading is likely to fall behind as the operation proceeds. For example, images are immediately displayed if the reading keeps up with the user operation, as in the case of switching from a screen in FIG. 10A (a screen in which images 1 to 6 are displayed) to the next screen, a screen in FIG. 10B (a screen in which images 7 to 12 are displayed). However, when the page is further switched in a short time to display a screen in FIG. 10C (a screen in which images 13 to 18 are displayed), the reading of images may fall behind. The dashed lines surrounding the images in FIG. 100 indicate that these images are not displayed yet because part of the processing of the display, such as the reading, has fallen behind. In such cases where the reading falls behind, it may be that no images are displayed as in FIG. 10C, and so the user does not obtain any hints as to what the displayed page, changed by the user's operation, represents. To know what the page represents, the user must wait for the completion of the reading of the images and the display of the images on the screen.
In the technique of document 1, generating the display image data at the time of recording images requires recording a large amount of display image data for display in an image recording medium, thereby requiring extra capacity in the medium. On the other hand, generating the display image data when images are displayed by a display device requires time for image generation in addition to the image reading time, thus requiring extra time in addition to the fundamental image reading time. This approach is also inconvenient in that a large area in a temporary memory device is necessary for generating and holding the display image data.
The technique of document 2 predicts the next page. Since image pre-reading is performed to read all images to be displayed in the predicted page, pre-reading over a wide range is not possible. Therefore, the technique is inconvenient in that the image reading speed soon falls behind in continuous page scrolling, resulting in no images being displayed on the screen.